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Cosmetic feature in start part

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Cosmetic feature in start part

In my old position we used a start part for all our new ProE parts. It had default datums planes etc., but we also had a cosmetic feature, a sketch of a circle about an inch in diameter. It was never used for anything, and at first I used to just delete it from my parts, and everyone else would jump on me and tell me to leave it in. Their explanation was that it affects the software's perception of the scale of the model or something. The idea is that even if the model becomes larger than the cosmetic feature, with the addition of later features, it somehow is pinned to a particular "regeneratability" because it started out as a particular size. (I never knew files had memory.) I should add our parts were mostly around hand-sized, so the cosmetic circle, while usually smaller than the final part, was never an order of magnitude smaller.

This always sounded like a load of dingo's kidneys to me, but after that discussion I would leave it in like a good boy, because it's not about me, is it?

Has anyone else heard of such a thing? Do you do something similar in your start part? I ask because I am making some templates for my current job and wonder if I should put this feature in it. Creo/Elements 5.0.

20 REPLIES 20

Re: Cosmetic feature in start part

I thought some people do that just because when they start sketching they want the sketch area to be closer to the size parts they are drawing.

I would think other then that, a better idea would be to turn and set absolute accuracy instead of relative.

Re: Cosmetic feature in start part

Until there is some geometry PTC defaults the part extents to something like 1000x1000x1000.

A circle 1 inch in diameter allows the software to evaluate the extents to about 1x1x1 which, for hand-sized parts, is a good choice. Being cosmetic, it doesn't affect much else and it used to be one could not use it as the basis for any other geometry, limiting the chances for building dependencies.

It's a reasonable thing to have in the start part to force some sense of proportion/scale/extents, which is what relative accuracy is gauged against.

I would put it and any other default geometry into a group called Default_geometry, so it can be compacted at the top of the feature tree. I've seen some models where half the screen space is take in default geometry, most of which isn't used.

Re: Cosmetic feature in start part

Matt Griswold wrote:

I thought some people do that just because when they start sketching they want the sketch area to be closer to the size parts they are drawing.

That makes sense. No reason not to delete it again afterwards, though.

I would think other then that, a better idea would be to turn and set absolute accuracy instead of relative.

Yep, we had that set too (in my old job, not here.)

Re: Cosmetic feature in start part

David Schenken wrote:

...

It's a reasonable thing to have in the start part to force some sense of proportion/scale/extents, which is what relative accuracy is gauged against.

...

Do you think though, that once you have started creating geometry you would no longer need that cosmetic and could delete it? I can't see how it could continue to influence the file when there are subsequent dimensioned features that are bigger.

Re: Cosmetic feature in start part

You could delete it, mostly harmlessly. I don't believe there is any geometry/software problem caused by deleting it. If there is a process built that depends on it by name or other characteristic, you'd have to care about that.

For example - screen positioning of a model - where it shows up on the screen - is dependent on the extents of the part/assembly. If you are doing screen caps of multiple configurations where the extents are affected, this can cause the model to shift location. If the cosmetic is set to be as large as the largest extents, then the model won't shift. If that curve is part of the screen cap process, then keeping it is a good idea.

Re: Cosmetic feature in start part

....not even a pile of foetid dingo's kidneys?? I'd actually considered doing that. And yes, I agree, that once you have actual geometry in there, you can detele it. Your coworkers are wrong, once other geometry is in there, the datums etc. scale to fit that. I don't buy the "memory" nonsense either. UNLESS it has something to do with the Relative accuracy, but I'm not even buying that. Anyone from PTC want to chime in on that?

There is actually a way to size your datums and axiis and that will drive the initial zoom, but then, the datums need to be resized, and it's more work doing all that than simply deleting one feature.

Glad you mentioned this, I was tempted to do this here.

Re: Cosmetic feature in start part

I was thinking about this some more. Years ago I took care of this just by opening the start part, scrolling in a bunch and saving the start part and it saved the position. I have NOT tried this anytime in recent years, so I do not know if that works any more.

Re: Cosmetic feature in start part

David Schenken wrote:

Until there is some geometry PTC defaults the part extents to something like 1000x1000x1000.

Is there a config setting to change this to something smaller like 50x50x50 or what ever one might designer? That should eliminate the need for a piece of geometry that will just be deleted later.

Re: Cosmetic feature in start part

Only one tip if those other yahoos are no longer in the picture:

  • Make your start parts and assemblies with -sized- datum planes.

This will limit the bounding box in a similar manner as the cosmetic sketch did.

With today's relative accuracy algorithm, this -should- not be an issue.

This may have been an oversight in the Creo Elements|WF5 offering.

I believe the relative accuracy implementation will always be a problem for new users and each will come up with what they believe is the "right" Pro|WorkAround^TM.

I have not had any issues with the initial bounding box of a new and empty part or assembly.

Once the 1st feature is created, a new bounding box is created.

You can easily investigate the bounding box size; in Creo 2 - Tools tab; Investigate; Model Size.

1st thing I do in a new sketch of a new part is to draw a 1" circle. Then I proceed with my sketch and later delete the circle. I do this because I no longer use start parts.

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